GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 GMC MD Steel Tilt (W Model) 🢒 Engine 🢒 Engine Controls - 5.0L and 5.7L 🢒 Fuel Tank Leak Test

Description

The fuel tank leak test is used to locate any fuel or fuel vapor escaping the fuel tank area. Fuel vapors escaping above the fuel level will be detected when the EVAP diagnostics completes one test cycle. The MIL will illuminate after the EVAP diagnostics completes two test cycles.

Diagnostic Aids
    • Operate the vehicle under the condition of the customers concern. Under high temperature conditions fuel vapors may increase to the point of EVAP canister vapor saturation. Fuel vapors would then be released into the atmosphere. Once the engine is running and EVAP purge is enabled, all fuel vapor release would be eliminated.
    • Test for fuel leaking in the following locations:
       - The fuel tank.
       - The fuel feed and return pipes.
    • Test for fuel vapor leaks in the following locations:
       - The fuel tank, fill limiter vent valve and rollover valves.
       - The fuel fill pipe, hose and fuel fill cap.
       - The fuel sender housing and seal.
       - The fuel tank pressure (FTP) sensor seal.
       - The EVAP vapor pipe.
    • Movement of the EVAP pipes or fuel pipes may help find an intermittent condition.

Test Description

  1. Perform this procedure to determine that no EVAP diagnostic DTC is present.

  2. This test is to locate fuel leakage in the fuel lines.

    3.

  3. This tests for fuel leaks below the fuel tank fuel level.

    4.

  4. This test is to locate fuel vapors escaping above the fuel level in the fuel tank .

Fuel Tank Leak Test

Step

Action

Yes

No

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Important: Before performing this procedure, place a dry chemical (class B) fire extinguisher near the work area.

  1. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General information.
  2. Inspect the fuel tank and fuel pipes for damage or external leaks.

Did you find fuel leaking from the fuel tank?

Go to Step 7

Go to Step 3

3

  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, command the fuel pump ON.
  3. Inspect for fuel leaking from the fuel pipes.

Did fuel leak from the fuel pipes?

Go to Step 8

Go to Step 4

4

  1. Install the J 41415-40 Fuel Tank Cap Adaptor.
  2. Connect the J 41413 EVAP Pressure/Purge Diagnostic station to the fuel tank cap adaptor.
  3. With a scan tool, seal the EVAP system.

    4. Important : Do not exceed 15 in H2O.

  4. With the EVAP pressure/purge diagnostic station, pressurize the fuel tank.

Did fuel leak from the fuel tank?

Go to Step 7

Go to Step 5

5

  1. With the EVAP pressure/purge diagnostic station, maintain pressure in the fuel tank.

    2. Important: It may be necessary to partially lower the fuel tank. Refer to Fuel Tank Replacement .

  2. With the J 41416 ultrasonic leak detector, test for leaks above the fuel level in the following locations.
    3. • The fuel tank, fill limiter vent valve, pressure relief valve and rollover valves. Refer to Fuel Tank Replacement .
    • The fuel sender housing and fuel sender seal. Refer to Fuel Sender Assembly Replacement .
    • The fuel tank pressure (FTP) sensor seal. Refer to Fuel Tank Pressure Sensor Replacement .
    • The EVAP vapor pipes. Refer to Fuel Tank Replacement .
    • The fuel fill pipe and hose. Refer to Filler Tube Replacement .

Did you locate a fuel leak?

Go to Step 6

Go to Diagnostic Aids

6

Repair the system as necessary.

Did you complete the repair?

System OK

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7

Replace the fuel tank. Refer to Fuel Tank Replacement .

Did you complete the repair?

System OK

--

8

Replace the leaking fuel pipe.

Did you complete the replacement?

System OK

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